What to do with a non fruiting blackcurrant bush

my daughter inherited ntwo blackcurrant bushes on her allotment. They appear to have some sort of disease, the leaves are gnarled and discoloured. Can we prune them back now or should we start again with new bushes?

Answers

i would start again with another less prickly plant.if you want any of this fruit its normaly growing somewear along lanes or road sides.saying that if its in the right place its a good diswader from vandals,thieves etc

I am confused ! prickly blackcurrant ! ! yes cut them right back then it would be a good idear to resite them with a little root pruning, just another part of your alotment , you will have a good crop next year.